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Date:      Thu, 06 Aug 2015 18:15:30 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-bugs@FreeBSD.org
Subject:   [Bug 202140] HP Z600 defaults to LAPIC for kern.eventtimer.timer but can't use 'Online CPU idle state' higher than C1 with this setting
Message-ID:  <bug-202140-8@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=202140

            Bug ID: 202140
           Summary: HP Z600 defaults to LAPIC for kern.eventtimer.timer
                    but can't use 'Online CPU idle state' higher than C1
                    with this setting
           Product: Base System
           Version: 10.1-STABLE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs@FreeBSD.org
          Reporter: brejoc@gmail.com

This computer is comsuming 160 watt when idle. I was looking for a way to
reduce that and was told to set 'hw.acpi.cpu.cx_lowest' to 'C3' or 'C8'.

If I'm setting 'hw.acpi.cpu.cx_lowest' to anything else than 'C1' the system
stops working properly. Applications just stop - waiting forever. This can very
easily be reproduced with ping. Starting to type anything on the shell "wakes"
the computer up and applications start to respond and work again. A clean
reboot is not possible with these settings.

Default for this computer for 'kern.eventtimer.timer' is 'LAPIC'. Allan Jude
from BSD Now, who was guiding me through the whole process, told me to try
'HPET', which worked. Both 'C3' and 'C8' for 'hw.acpi.cpu.cx_lowest' are now
possible without any downside effects.

Power consumption is down to around 90 watt with 'C8' and the system is working
flawlessly and stable. Thanks Allan, Kris and last but not least TJ!


But it would be much nicer, if this would work right out of the box!




Some additional information:

--- Xeon E5520 ---

$ sysctl hw.|head
hw.machine: amd64
hw.model: Intel(R) Xeon(R) CPU           E5520  @ 2.27GHz
hw.ncpu: 8
hw.byteorder: 1234
hw.physmem: 8545079296
hw.usermem: 8300666880
hw.pagesize: 4096
hw.floatingpoint: 1
hw.machine_arch: amd64
hw.realmem: 8592031744


--- Event timer choices ---

$ sysctl kern.eventtimer.choice
kern.eventtimer.choice: LAPIC(400) HPET(350) HPET1(340) HPET2(340) HPET3(340)
i8254(100) RTC(0)

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